This invention relates to catalysts with which volatile sulfur compounds can be removed substantially completely from industrial gases, to a process for the production of these catalysts and to their use for the removal of sulfur compounds from industrial gases.
Sulfur-containing compounds such as, for example, carbon oxysulfide, carbon disulfide and hydrogen sulfide are common impurities of industrial gases such as, for example, carbon monoxide, carbon dioxide, nitrogen, methane and natural gas. They are formed, for example, in the processing of sulfur-containing gaseous, liquid or solid starting materials, such as natural gas, petroleum, coke and coal.
The removal of such sulfur-containing constituents from industrial gases is often necessary, for example in view of catalyst damage, corrosion, unwanted secondary reactions in the organic and inorganic synthesis and also in view of the high toxicity of the sulfur-containing components, even in low concentrations.
Whereas hydrogen sulfide as the most common impurity of carbon oxysulfide and carbon disulfide can be removed from gases by a number of known processes, the simultaneous removal of carbon oxysulfide and carbon disulfide from gases is problematical.
Adsorbents, such as active charcoal, zeolites or silica gel, are generally known to have only a very low adsorption capacity for carbon oxysulfide and carbon disulfide. The purification of gases, for example by washing with liquid basic media, involves considerable effort because the solubility of carbon oxysulfide and carbon disulfide in such media is minimal. In addition, working up of the spent solutions involves environmental problems.
According to JP 247 084, heavy metals of the first, second and eighth secondary groups of the periodic system and lanthanide elements are added to lignite as a support material. The catalyst obtained in this way is capable of adsorbing sulfur-containing compounds from industrial gases and desorbing them again at a later stage. In this case, however, the sulfur-containing components do not react chemically to form sulfur compounds readily removable from a gas mixture, so that desorption of the sulfur-containing components leaves a gas mixture enriched with toxic sulfur compounds which is ecologically undesirable.
Processes in which carbon oxysulfide and carbon disulfide are converted into hydrogen sulfide on solid media, generally zeolites, aluminium oxide and the like, and the hydrogen sulfide formed is subsequently removed from the gas mixture by known methods have been adopted for practical application.
The disadvantage of such processes lies in their high energy consumption because the conversion of carbon oxysulfide or carbon disulfide only takes place at high temperatures, generally of the order of 400.degree. to 800.degree. C.
A process for the removal of carbon oxysulfide from gases which is known from DE-A-1 667 590 uses certain heavy metal oxides as catalysts on active charcoal as support. This process has many disadvantages on account of the abrasion of the charcoal and its combustibility.
In addition, it is known from DE-A 2 203 494 that aluminium oxide containing molybdenum, iron, tungsten, nickel or cobalt or certain combinations of these metals can be used as a catalyst for the reaction of carbon oxysulfide with steam. These metals are generally used in the form of sulfides. However, uneconomically high temperatures of 250.degree. to 400.degree. C. are required for the hydrolytic reaction of carbon oxysulfide and carbon disulfide.